PSI - Issue 60

Prakash Bharadwaj et al. / Procedia Structural Integrity 60 (2024) 655–664 Prakash Bharadwaj / Structural Integrity Procedia 00 (2019) 000 – 000

659

5

( , )= + + ( , )= + +

(3)

(4)

Where = 0∗ − 0 , = 0∗ − 0 , = − 0 and = − 0 . The strain components obtained by the Lagrange strain tensor are as follows: = 12 2 , = 12 2 , =1 2( + ), = =0 Using strain components, Von Mises's equivalent yield strain is calculated by equation 5. = √32 √( − ) 2 +( − ) 2 +( − )2 +6( 2 + 2 + 2 )

(5)

Fig. 3. Reference and deformed subzone for DIC calculation

4.2 Use of load-strain curve for estimation of cyclic plastic zone Fig. 4(a) shows a typical plot of cyclic and monotonic plastic zones ahead of crack tip. Here three points p, q, and r are selected in different regions such that point p is located within the CPZ, while points q and r are located within the MPZ and elastic zone, respectively. Fig. 4 (b) plots typical stress-strain hysteresis curves at these points. It may be noted that at point p the hysteresis loop opens (indication of cyclic plastic strain range), while the hysteresis plot at points q and r does not open, an indication of monotonic yielding and elastic cycling respectively. The reason for the hysteresis loop opening is the reverse yielding at point p. Thus, by observing the stress-strain